[Wien] Possible technical error in telnes

[Laurence Marks]

From what I can see, it appears that telnes3 is ignoring the absolute
energy range that the user inputs. In a case I just ran to look at an O K
edge it did not matter whether I used 500-530 as the energy range or
520-550, in both cases the EELS zero was the same and the spectra looked
identical. [1]

Of course the absolute edge position is dodgy. However, I am interested in
relative shifts for different atoms in a single structure. I will argue
that at a minimum the core energy should be reported in the spectrum output
file. (I will probably hack my version to do this.)

[1] My energy range got cut to 10 eV as I did not go high enough in lapw1,
but this should not matter.

[Laurence Marks]

I agree with your comments about 2)-3).

What I noticed is that telnes3 has as the energy origin the difference in
energy between the core state (calculated internally by a clone of lcore
using case.inc for occupancies) and the Fermi energy. This number is not
output anywhere within telnes3. While it is not hard to do a manual
correction afterwards, I argue that this number should be included in the
output.

N.B., there might be another issue if one uses a spin-polarized core hole
since x telnes3 uses case.inc; I have not tested but wonder.

I'm not running elnes very often, and I also do not really understand
In the input you enter an energy range from zero (=EF) to something.
This means all spectra (of different O-atoms) start at zero and possible
shifts should be evident.
You also enter an edge onset, which could be taken as the corresponding
core eigenvalue-EF (although this is a very bad estimate of the core
binding energy - and excitonic effects will change this also.
The shift (relative positions) of 2 O-atoms in the same compound could
1)different position of O-p states in the conduction band
2)different core BE
2)different excitonic effect.
1) is trivial and should come out of the simulations
2+3 are much more difficult to estimate. The groundstate core-energies
will most likely not give proper corelevel shifts and no excitons.
You can do several core hole calculations, which for an insulator are
usually mandatory anyway. The core energies of such calculations are too
low (that would require more half a core-hole), but excitonic effects
might be covered partially.

Post by Laurence Marks
From what I can see, it appears that telnes3 is ignoring the absolute
energy range that the user inputs. In a case I just ran to look at an O
K edge it did not matter whether I used 500-530 as the energy range or
520-550, in both cases the EELS zero was the same and the spectra looked
identical. [1]
Of course the absolute edge position is dodgy. However, I am interested
in relative shifts for different atoms in a single structure. I will
argue that at a minimum the core energy should be reported in the
spectrum output file. (I will probably hack my version to do this.)
[1] My energy range got cut to 10 eV as I did not go high enough in
lapw1, but this should not matter.
--
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what
nobody else has thought", Albert Szent-Gyorgi
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Post by Laurence Marks
Co-Editor, Acta Cryst A
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